An IQ-signal consists of two orthogonal signal parts with identical amplitude, namely an I-part (in-phase) and a Q-part (quadrature), whereby the I-part leads the Q-part by 90° in case of positive frequencies and lags the Q-part by 90° in case of negative frequencies. Thus an IQ-signal can also be considered as a complex signal, the I-part representing the real part and the Q-part representing the imaginary part.
IQ-signals are very often used in signal processing; for instance for modulation methods, in which the required bandwidth can be halved by using IQ-signals, or for speed measurement via Doppler shifting in pulse reflection methods, not only the value of the relative speed but also the sign thereof can be determined by using IQ-signals.
For generating IQ-signals, it is conventionally known to use a complex mixer consisting of two orthogonal real mixers, up to the present date. That adds to the complexity and expense of circuit arrangements for generating IQ-signals